Research News Archive 2012

Genetic association study of glucocerebrosidase gene L444P mutation in essential tremor and multiple system atrophy in mainland.

Researchers from the Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China, studied a gene mutation in glucocerebrosidase (GBA) that is emerging as an important risk factor for Parkinson’s disease (PD).

The researchers previously reported that the GBA gene L444P mutation is an important risk factor for PD in the Chinese population. The prevalence of this mutation in other neurodegenerative diseases and movement disorders remains completely unexplored in mainland China.

In the study, 109 Chinese patients with essential tremor (ET), 54 patients with multiple system atrophy (MSA), and 657 control subjects were screened for the GBA gene L444P mutation.

None of the 109 patients with ET or 54 patients with MSA carried the GBA gene L444P mutation.

The difference in mutation frequencies between patients with ET or MSA and the control group was not statistically significant. The results suggest that the GBA gene L444P mutation may be not responsible for ET in mainland China. Whether the GBA gene L444P mutation modifies the risk for MSA deserves further study in larger samples.

Published in the Journal of Clinical Neuroscience, November 2012.

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Reliability of a new scale for essential tremor
Results of a study published in Movement Disorder (2012, Oct 2) examined the reliability of a new scale for the clinical assessment of essential tremor. The Essential Tremor Rating Assessment Scale contains 9 performance items that rate action tremor in the head, face, voice, limbs, and trunk from 0 to 4 in half-point intervals. Head and limb tremor ratings are defined by specific amplitude ranges in centimeters.

METHODS:
Videos of 44 patients and 6 controls were rated by 10 specialists on 2 occasions 1-2 months apart. Inter- and intrarater reliability was assessed with a 2-way random-effects intraclass correlation, using an absolute agreement definition.

RESULTS:
Inter- and intrarater intraclass correlations for head and upper-limb tremor ranged from 0.86 to 0.96, and intraclass correlations for total score were 0.94 and 0.96. The intraclass correlations for voice, face, trunk, and leg were less robust.

CONCLUSIONS:
This scale is an exceptionally reliable tool for the clinical assessment of essential tremor. © 2012 Movement Disorder Society.

Adoption and use of this tool could provide a more reliable, accurate, and consistent assessment of essential tremor by healhcare professionals.

Researchers Study Effect of Low-Frequency Magnetic Stimulation on Brain for People with Essential Tremor

Overview
Results of a study published in Brain Stimulation (May 2012) indicate that low-frequency repetitive magnetic stimulation of a region of the brain may reduce essential tremor for a prolonged period.

Research
Researchers in Paris, France applied low-frequency (1 Hz) repetitive transcranial magnetic stimulation (rTMS) to the cerebellum in order to modulate the movement that causes tremor in ET. Researchers observed that one session of rTMS induces a brief improvement. They hypothesized that repeated sessions might have a cumulative and potentially long-term therapeutic effect on ET. In the trial, the researchers assessed the effects of a one-week treatment on tremor for eleven patients with ET and eleven control subjects.

Results
Repeated rTMS over the cerebellum significantly improved assessment scores for tremor, drawing, and functional disability. The treatment also reduced tremor amplitude. The effects persisted for 3 weeks after the last session.

Conclusion
Cerebellar stimulation could be an effective treatment option one day for patients with severe essential tremor.

Considerations
This trial is an extremely small sample of patients. rTMS is not available now as an ET treatment. It is not clear how long the effects of rTMS will last.

Published in Brain Stimulation, 2012 May 12.

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Gaba and serotonin molecular neuroimaging in essential tremor: A clinical correlation study
Researchers from the Movement Disorders Unit, Department of Neurology, Sant Pau Hospital in Barcelona Spain studied the gabaergic system in relation to essential tremor. The results were published in Parkinsonism Related Disorders, 2012 May 15.

Gabaergic refers to transmitting or secreting gamma amino butyric acid (Gaba), an amino acid that occurs in the central nervous system and is associated with the transmission of nerve impulses.

In relation to essential tremor there is some consensus about the involvement of the cerebellum and accumulating evidence points towards a dysfunction of the gabaergic system. The researchers hypothesize that the serotonin neurotransmission system may also play a role as it does in tremor in Parkinson disease. Serotonin is a chemical the body produces that’s needed for nerve cells and brain to function.

This study aimed to investigate the association between the severity of tremor symptoms and the gabaergic and serotoninergic neurotransmission systems in essential tremor.

After ten patients were studied, the researchers concluded that the severity of tremor correlated with the abnormalities found in GABA receptor binding. This suggests a primary gabaergic deficiency or a functional abnormality with GABA(A) receptor subtypes. These results may assist in the rational development of new pharmacological treatments for essential tremor.

Great Lakes NeuroTechnologies Tackles Continuous Monitoring of Essential Tremor with Launch of Multi-Site Clinical Study
Great Lakes NeuroTechnologies announced in April 2012 that they have launched a multi-site clinical study to assess continuous monitoring of essential tremor (ET) using their Kinesia technology platform. A preliminary study published in 2011 in the journal Parkinsonism and Related Disorders demonstrated that patient-worn motion sensors could detect tremor type and quantify tremor severity during both standardized tasks and nonstandardized activities of daily living performed in a laboratory. Now the company is expanding those results to sixty subjects with ET as they go about their daily lives in their homes. The study, which is funded by the National Institutes of Health, is being conducted in partnership with Dr. Christopher Goetz of Rush University Medical Center in Chicago, Illinois and Dr. Joseph Jankovic of Baylor College of Medicine in Houston, Texas.

Color vision: a study of essential tremor cases versus normal controls
Background and purpose: Patients with essential tremor (ET) and Parkinson’s disease (PD) may exhibit overlapping clinical features. Also, a growing number of non-motor features are being documented in ET. Color vision abnormalities, although well known to occur in PD, have not been studied extensively in ET. We assessed color vision in ET cases and controls. We furthermore assessed subgroups of ET cases with clinical features that might link them to PD (i.e., ET cases with a family history of PD, and ET cases with rest tremor) to determine whether these cases had greater color vision abnormalities than ET cases without those features.

Conclusions: Although a number of links exist between ET and PD, and non-motor features have been described in both, a color vision abnormality does not seem to be a feature of ET.

© 2012 The Author(s). European Journal of Neurology © 2012 EFNS.
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